Process for manufacturing compressed asphalt blocks.



G. B. UPHANL.

PROCESS FOR MANUFACTURING COMPRESSED ASPHALT BLOCKS.

APPLICATION FILED JULY 5.1910.

1,168,758 Patented Jan. 18, 1916.

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GEORGE E. UPHAM, 013 BOSTON, MASSACHUSETTS.

PROCESS FOR MANUFACTURING COMPRESSED ASPHALT BLOCKS.

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' Application filed July 5,

. To all whom it may concern:

- the following is a specification.

This invention relates to a process for treating material in the manufacture of blocks or tiles from asphaltic or other bituminous compositions.

In order that my invention may be readily understood, I shall describe its use in connection with the usual process of manufacturing asphaltinblocks.

Compressed asphaltic paving blocks are I manufactured from crushed and pulverized stone united by a bituminous binder. A formula frequently used employs between seventyfive and eightyfive per cent. of crushed rock, between five and ten per cent.

of Trinidad asphalt and from ten to fifteen per cent. of pulverized limestone, commonly called fines. .Thc crushed rock of this mixture is heated to about 350 1 the asphaltic cement to about 320 F., the ingredients are thoroughly mixed, fed toa press and are there, at a temperature of about 290 F. subjected to heavy compression in a suitable mold.

On issuing from the press such blocks are frequently more or less cracked by the expansion of air or gas trapped in the block during the compressing action. The material is fed down the elongated neck of the press in a loose or coarsely granular condition. A certain depth of this material, for instance, 4%", is allowed to fall into the mold for each block. The mold is then covered by a suitable plate and heavy pressure is applied to compress the material. \Vhen the depth of li'ose material is 4% and pres sure is applied, a comparatively solid block of about 3 thickness is formed. As the ingredients are practically incompressible, it is clear that the 19; reduction in volume is caused by the expulsion of the hot air or gases from the interstices of the"m'ixture. This expulsion is not completehowever. As the plunger moves up from below it presses the mass against theplateabove. Those portions of the; material near the plunger and near the plate are believed to be the first to be affected by the compression. This solidifies'them to some extent almost imme- Specification of Letters Patent.

Patented Jan. 18, Tahiti.

1910. Serial No. 570,266.

diately and renders it dii'licult for the air in the center of the mass to escape through the small openings around the top and bottom edges of the mold. Most of the air escapes, but some is trapped, which, being subjected to say six thousand pounds pressure to the square inch, is tremendously reduced in volume. As soon as t-he pi'essure is remoi'ed thistends to expand and in so doing and in escaping to the surface tends to crack sonic what the structure of the block.

The drawings illustrate diagrammatically one embodiment of my new process. Figure 1 shows relative positions of the mold, mold cover, neck and plunger, prior to filling; Fig. 2 shows the relative positions thereof after filling; Fig. 2: shows the relative positions thereof after open mold compressionpFig. -1- shows the relative positions when ready for final compressing; Fig. 5 shows the'relative positions after compression; Fig. 6 shows the relative positions after the mold has been emptied.

My new process aims to decrease this tendency to crack by driving off a large percentage of the hot air or gases from the granular material prior to the application of pressure thereto in the closed mold. For this purpose I provide means whereby, after material has been allowed to fill the mold and while the mold is open to the feeding neck which is still above in communication and in register With. the incomplete mold. that is to say, the mold without a cover, the lower wall or plunger of the mold is raised to compress the material in the mold. from beneath against the column of material above it in the neck, thus forcing the hot air or gases upwardly in the direction in which they naturally tend to go. This column, though open at the top, offers considerable resistance to the compression of the mate rial by reason of its Weight and its frictional contact with the inner surfaces of the neck. The result ofthis upward pressure is to solidify to some extent the material by driving out the hot air and gases. These escape with comparative readiness, some through the slits or joints Where the neck .and the plunger meet the mold and some throughthe porous column of the material in the neck above, which receives the pressure in place of'the solid plate as has been the case heretofore. The lower part of the column of material in the neck also may have some of the air-driven from it when it receives the upward pressure and in such case less air remains to be expelled when it in its turn reaches the mold. Subsequently the material so treated in the mold is segregated from the column and, after the mold has been completed or covered, issulnected to one or more compressions therein, and subsequently e ected and cooled at a relatively low temperature in the usual manner preferably in water.

The thickness of the resultant block may be determined by the upward limit of the preliminary open mold com ression' stroke if it is desired to do so. I this stroke is regulated in such manner as to cause its-upward limit to be high, a larger percentage of the material which entered the mold on .enough material will be left in the mold to the downward stroke of the plunger may be' forced back into the lower portion of the neck and hence a thinner block Wlll be formed. Conversely if the plunger stroke is regulated in such a manner as to'cause its upward limit to be low in the mold, a smaller percentage or none of the-material will be forced up into the neck and hence form a thicker block after final compression.

It will be understood that when-reference is made in the claim to opposing to such compression the resistance of the portion of the column above the mold, this resistance includes such frictional resistance as may be caused by the contact of the material of the column with the inner surface of the neck. v

In the claims I have used the expression applied compression. By this I mean.

pressure applied tozthe column of material automatically, by fluid p-ressure or mechanical means, as distinguished from gravity or pressure from above imparted by hand. The action of gravity is not suflicient. to expel much of the-air from the mass", and hand pressure, such as is sometimes'- -,imparted bv sticks to force the materialdown the neck, has thefopposite effect from'that I which is desired. It tends to solidify to some extent the material on the top of the rial above remains sufficiently porous to allow the comparatively free escape of the air. i

I have found that a block compressed from material treated by my process has much less tendency to crack than a block made bv the ordinary process, because of the smaller quantity oi air entrapped therein.

My invention is not confined to the specific manner of practising it above described. What I claim and desire to secure by Letters Patent is:

The process of bituminous paving blocks which consists in forming a prolonged, confined .column of heated bituminous material, the lower portion of said column being of substantially IS constant cross sectional dimensions, the lower end of said column resting in a mold; compressing from-beneath the lower end of said column that'is in the mold, thereby expelling entrained air through said column.

while opposing to such compression the re-' slstance ofaportion of the column above the mold; dividing the column transversely,

adjacent the top of the moldand covering the latter; subjecting the covered contents $5 of the mold to final compressionto produce the compressed block, and cooling the compressed block to preserve its shape.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

GEORGE B. UPHAM.

Witnesses I PRESTON UPHAM, Roenn'r H. KAMMLER.

By my 50 the mold, so that; 55

e 70 manufacturing compressed 

